When meet "The Module DLL C:\Windows\System32\inetsrv\isapi.dll failed to load. The data is the error." message in event log

When 503 Sevice unable error occured, check event viewer.
If you see "The Module DLL C:\Windows\System32\inetsrv\isapi.dll failed to load.  The data is the error." message, try this one.

[Error Message]

[solution]